Lithography

About: Lithography is a research topic. Over the lifetime, 23507 publications have been published within this topic receiving 348321 citations.

Biomimetic subwavelength antireflective gratings on GaAs.

Abstract: We have developed a simple and scalable bottom-up approach for fabricating moth-eye antireflective coatings on GaAs substrates. Monolayer, non-close-packed silica colloidal crystals are created on crystalline GaAs wafers by a spin-coating-based single-layer reduction technique. These colloidal monolayers can be used as etching masks during a BCl3 dry-etch process to generate subwavelength-structured antireflective gratings directly on GaAs substrates. The gratings exhibit excellent broadband antireflective properties, and the specular reflection matches with the theoretical prediction using a rigorous coupled-wave analysis model. These bioinspired antireflection coatings have important technological applications ranging from efficient solar cells to IR detectors. © 2008 Optical Society of America OCIS codes: 050.2770, 220.4241, 310.1210, 310.6628. Gallium arsenide (GaAs) is a technologically important semiconductor that has been widely used in optoelectronics, such as vertical cavity surface-emitting lasers [1], near-IR photodetectors [2], and highly efficient concentrator solar cells [3‐5]. However, owing to the high refractive index (RI) of GaAs (nGaAs3.6 for visible wavelengths), more than 30% of incident light is reflected back from the substrate surface. This greatly reduces the efficiency of GaAs-based optoelectronic devices. To suppress the unwanted reflective losses, vacuum-deposited multilayer dielectric (e.g., MgF2/ZnS antireflection coatings (ARCs) have been developed [6,7]. Unfortunately, these multilayer ARCs are expensive to fabricate owing to the stringent requirement of high vacuum, material selection, and layer thickness control. Additionally, thermal-mismatch-induced lamination and material diffusion of the multilayer ARCs limit the device performance at high power densities [3]. Inspired by the broadband antireflection of microstructured corneas of moths, which consist of nonclose-packed arrays of sub-300 nm nipples [8], subwavelength antireflective structures have been extensively exploited [9‐17]. These structures can reduce reflection over a wider range of wavelengths and exhibit much improved thermal stability than conventional multilayer ARCs. However, scalable production of subwavelength ARCs is not a trivial task for the current top-down nanolithography technologies (e.g., electron-beam lithography and interference lithography) [11,13]. Bottom-up colloidal lithography, which uses self-assembled colloidal crystals as deposition or etching masks to pattern periodic nanostructures [18,19], provides a much simpler and inexpensive alternative to nanolithography in creating subwavelength gratings [16,20]. Unfortunately, traditional colloidal assemblies suffer from low throughput, small areas, incompatibility with standard microfabrication, and limited close-packed crystal structures.

Lithographic printing members having secondary ablation layers for use with laser-discharge imaging apparatus.

Abstract: Lithographic printing plates suitable for imaging by means of laser devices. Laser output ablates one or more plate layers, resulting in an imagewise pattern of features on the plate. The image features exhibit an affinity for ink or an ink-abhesive fluid that differs from that of unexposed areas. The plates also include a secondary ablation layer that ablates only partially, and in a controlled fashion, as a result of destruction of overlying layers.

A review of excimer laser projection lithography

Abstract: Excimer‐laser projection lithography now appears to be in a position to extend production optical techniques to dimensions approaching 0.25 μm. Such methods could well be the basis for the bulk of the advanced manufacturing capability in microelectronics over the next decade. This technology is reviewed with an eye to the state of the art and to the optical‐, resist‐, and materials‐engineering issues that it presents.

Mechanical Properties Tunability of Three-Dimensional Polymeric Structures in Two-Photon Lithography

Abstract: Two-photon (2P) lithography shows great potential for the fabrication of three-dimensional (3-D) micro- and nanomechanical elements, for applications ranging from microelectromechanical systems to tissue engineering, by virtue of its high resolution (<100 nm) and biocompatibility of the photosensitive resists. However, there is a considerable lack of quantitative data on mechanical properties of materials for 2P lithography and of structures obtained through this technique. In this paper, we combined static and dynamic mechanical analysis on purpose-designed microstructures (microbending of pillar-like structures and picometer-sensitive laser Doppler vibrometry of drum-like structures) to viably and nondestructively estimate Young's modulus, Poisson's ratio, and density of materials for 2P lithography. This allowed us to analyze several polymeric photoresists, including acrylates and epoxy-based materials. The experiments reveal that the 2P exposure power is a key parameter to define the stiffness of the realized structures, with hyperelasticity clearly observable for high-power polymerization. In the linear elastic regime, some of the investigated materials are characterized by a quasi-linear dependence of Young's modulus on the used exposure power, a yet unknown behavior that adds a new degree of freedom to engineer complex 3-D micro- and nanomechanical elements.

Photonic band-gap formation by optical-phase-mask lithography.

Abstract: We demonstrate an approach for fabricating photonic crystals with large three-dimensional photonic band gaps (PBG's) using single-exposure, single-beam, optical interference lithography based on diffraction of light through an optical phase mask. The optical phase mask (OPM) consists of two orthogonally oriented binary gratings joined by a thin, solid layer of homogeneous material. Illuminating the phase mask with a normally incident beam produces a five-beam diffraction pattern which can be used to expose a suitable photoresist and produce a photonic crystal template. Optical-phase-mask Lithography (OPML) is a major simplification from the previously considered multibeam holographic lithography of photonic crystals. The diffracted five-beam intensity pattern exhibits isointensity surfaces corresponding to a diamondlike (face-centered-cubic) structure, with high intensity contrast. When the isointensity surfaces in the interference patterns define a silicon-air boundary in the resulting photonic crystal, with dielectric contrast 11.9 to 1, the optimized PBG is approximately 24% of the gap center frequency. The ideal index contrast for the OPM is in the range of 1.7\char21{}2.3. Below this range, the intensity contrast of the diffraction pattern becomes too weak. Above this range, the diffraction pattern may become too sensitive to structural imperfections of the OPM. When combined with recently demonstrated polymer-to-silicon replication methods, OPML provides a highly efficient approach, of unprecedented simplicity, for the mass production of large-scale three-dimensional photonic band-gap materials.